You can rent a taxi to get around Singapore, but little expensive. So I suggest using MRT. You can buy EZ link card from any MRT station any use it in buses, MRT or LRT services as well as some taxis. All key attractions are within walking distance from an MRT station, so it's the fastest way to explre the whole city. The Singapore Tourist Pass for an adult comes in 3 options - 1-day pass costs $10, 2-day pass costs $16 and 3-day pass costs $20. So choose the one that suits your plan and buy it. But don't miss the opportunity to visit China Town, Gardens by the Bay, Sentosa Island and Universal Studios.